It is known that many diamines are useful as chain extenders or diisocyanate precursors in the preparation of polyurethane, polyurea, and polyurethane-urea polymers and as curing agents for epoxy resins. It is also known that cycloaliphatic diamines are apt to have the advantage of providing more color-stable products and that slower reacting diamines are sometimes desired to permit adequate time for processing.
It would be desirable to provide sterically hindered 1,3-diaminocyclohexanes which could be used in the aforementioned applications. However, most known processes for preparing cycloaliphatic amines from aromatic amines lead to such excessive hydrogenolysis in the hydrogenation of sterically hindered aromatic amines that the yield of diamine product is unacceptably low.
U.S. Pat. Nos. 3,697,449 (Brake) and 3,914,307 (Massie) show that some alkyl-substituted diaminocyclohexanes, viz., 1,4-diamino-2-methylcyclohexane, 1,3-diamino-2-methylcyclohexane, 1,2-diamino-3-methylcyclohexane, 1,3-diamino-2-methyl-4-ethyl-5,6-dipropylcyclohexane, are known; and Brake further teaches that cycloaliphatic amines can be prepared by the hydrogenation of aromatic amines in the presence of a supported ruthenium catalyst and an activating amount of an alkali metal hydroxide or alkoxide.